Commissioning and Operation of SUPER - CELLS...1 7th ESLS RF Workshop 16-17 October 2003 SUPER-3HC at Elettra M.Svandrlik Commissioning and Operation of SUPER-3HC at ELETTRA M. Svandrlik

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7th ESLS RF Workshop16-17 October 2003

SUPER-3HC at ElettraM.Svandrlik

Commissioning and Operation of SUPERCommissioning and Operation of SUPER--3HC3HCat ELETTRAat ELETTRA

M.M.SvandrlikSvandrlik

•Last year history and system overview•Commissioning and Operational Experience•Lifetime increase and Landau damping•Effect of a gap in the bunch train•Outlook and Conclusions

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•August - September 2002: INSTALLATION•October - December 2002: Cryogenic System

Commissioning and Warm Cavity SR operation

What happened in the last yearWhat happened in the last year

•January 2003: Cavity cool-down and first operation with beam.

•February - June 2003: cavity commissioning with beam while operating the storage ring for user’s.

•Since July 2003: standard cavity operation for user’s shifts established.

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Overview of the SystemOverview of the System

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Commissioning ExperienceCommissioning Experience� Quite tricky faults on the system have been solved:

a) Leak on the insulation vacuum of the cold He gas return line (02/2003)

b) Replacement of the under vacuum, cold tuning system (06/2003)

� System stops due to external reasons are not included in the above statistics:� 3 stops due to electrical power interruptions caused by thunderstorms

� 2 stops caused by electrical power blackouts (on 28/09 Italian blackout)

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RUN 81 RUN 82 RUN 83 RUN 84 RUN 85 RUN 86 RUN 87

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User downtime due to 3HC,% Total down time due to 3HC,%

3HC COMMISSIONING 3HC Normal Operation

Cold He line

Tuning System

Run 84 and 85:Run 84 and 85:No user downtimeNo user downtimeFine tuning of Maintenance and Start-up Proceduresto remove the causes of downtime during the machine shifts of these runs.

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Operational ExperienceOperational Experience� Operation

1) The cavity is parked during injection and energy ramping

�� Standard Settings Standard Settings

�� 33rdrd harmonic frequencyharmonic frequency 1498.955 MHz�� Cavity frequency at 320 mACavity frequency at 320 mA 1499.015 MHz�� Parking PositionParking Position 1499.200 MHz�� ∆∆∆∆∆∆∆∆ff at 320 mAat 320 mA +60kHz�� Nominal Voltage per cellNominal Voltage per cell 300 kV

2) The voltage is build-up in the cavity by tuning it at the end of the ramping.3) A slow voltage feedback keeps the voltage constant for the first part of the

current decay, from 320 mA down to 230 mA. Then it stops.

�� No instability driven by 3HC during injection, ramping and operNo instability driven by 3HC during injection, ramping and operationation

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Bunch lengthening experimentBunch lengthening experiment

The theoretical voltage build-up in the cavity, for Ib = 300 mA, shows that in the detuning region between 70 and 65 kHzthe voltage should approach about 1/3 of the main RF voltage (1,7 MV).

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050100150200250300Detuning, ∆∆∆∆f (kHz)

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Third Harmonic Voltage

V=Ib (R/Q) f3H/∆∆∆∆f

This measurement is performed at 2,0 GeV, 300 mA. The measured fs decreases with the detuning; at ∆f = 67 kHz, fs is 3,5 kHz, which corresponds to an average elongation factor 2,9.

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Lifetime and Landau damping in the same experimentLifetime and Landau damping in the same experiment

In the same experiment, before activating the cavity, the beam the beam performs strong longitudinal performs strong longitudinal oscillations (20oscillations (20--23 23 degdeg).).Lifetime is about 20 hoursLifetime is about 20 hoursDue to the strong bunch dilution it is much higher than the theoretical value for this optics, 7,7 hours.7,7 hours.

Activating the cavity, when the average elongation factor reaches 3, the the longitudinal oscillation is Landau longitudinal oscillation is Landau damped.damped.

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THE BEAM IS STABLETHE BEAM IS STABLE(transverse feedbacks are ON)

LifetimeLifetime isis increasedincreased toto 27 hours27 hoursHence the gain factor to the theoretical value is

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By comparing a typical day with the 3rd harmonic tuned (beam longitudinally stable) to a day when it is parked (controlled longitudinal excitation) one can seethat the final current, before dumping the beam, is doubled when the cavity is active.

180 mA

90 mA

A typical day at 2.0 A typical day at 2.0 GeVGeV, User’s Mode, User’s Mode

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Benefits of large lifetime: last week at 2 Benefits of large lifetime: last week at 2 GeVGeV

27 hours 36 hours 80 hours

• On the 1st day, 27 hours between two injections (as usual for the 1st day, then every 24 hrs)

• On the 2nd day, the users decided for injections every 36 hours, due to the large lifetime.• In the following 3 days, in fact no injections due to a linac fault, now solved. The users

could however work with a reasonable beam current intensity; 80 hrs without injecting.

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During the 2.4 GeV period scheduled for the first part of the present run 86 the cavity has been activated also at this energy, where the current is limited to140 mA, due to vacuum chamber thermal load limitation.

90 mA

65 mA

A typical day at 2.4 A typical day at 2.4 GeVGeV, User’s Mode, User’s Mode

At this current, for safe operating conditions we must stop at +43 kHz detuning. The 3rd harmonic voltage is then about 350 kV, i.e. 60% of the nominal voltage.

Nevertheless the typical beam lifetime attains 45-50 hours, that means a 50%improvement to the lifetime with parked cavity (where at 2.4 GeV, 140mA the beam is already stable).

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I=320mA, f3HC = 1499.015 MHz

The streak camera measurements allow to characterise the phase modulation along the bunch train when a gap is present. At ELETTRA a gap of about 43empty buckets in the 432 bucket of the ring allows to clear trapped ions (10%,i.e. 86 ns gap).

This gap induces a phase modulation along the bunch train.

Gap ~ 10%

432 buckets = 864ns

Effect of a gap in the bunch trainEffect of a gap in the bunch train

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The Streak Camera data elaboration shows that the phase shift “head-tail” is about 30deg and the bunch length changes from almost 76ps to about 32ps, with an average lengthening factor ~ 3.

Bunch phase and length along the trainBunch phase and length along the train

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OutlookOutlook

•In the November shutdown we will replace one of the two gate valves on the beam tubes.

•In January 2004 we will perform the first general maintenance of the system.

•To decrease the number of system interruptions we are planning to connect the compressor station to a UPS.

•We are considering the possibility of installing a Helium recovery system, which would be then used by all cryogenic systems at ELETTRA.

•• Further studies on the effects of gaps in the bunch train and on Landau damping are considered, possibly also in collaboration with the ESRF.

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ConclusionsConclusions

•The cryogenic plant and the cavity have been successfully commissioned.

•Since July 03 the cavity is routinely running during the standard user’s operation mode.

•At 2.0 GeV, 320 mA with active cavity the lifetime attains 27 hours, that is the lifetime is increased by a factor 3.5.

•For the first time it has been possible at Elettra to deliver a completely stable beam at 2.0 GeV, 320 mA.

•Characterisation studies of the effect of an empty gap in the train have been started.

Documents

Commissioning and Operation of SUPER - CELLS...1 7th ESLS RF Workshop 16-17 October 2003 SUPER-3HC at Elettra M.Svandrlik Commissioning and Operation of SUPER-3HC at ELETTRA M. Svandrlik